Balloon catheter with stiffening wire transition

ABSTRACT

A balloon dilatation catheter has a relatively stiff and strong proximal cannula made of a material such as for example metal hypotubing. The distal end of the catheter includes an inflatable medical device or balloon, an inflation lumen and a guidewire lumen. A transition assembly is positioned between the proximal cannula and the distal end section. This transition assembly has a stiffening member within a transition tube, and provides for a flexible transition between the two components of diverse stiffness, namely the proximal cannula and the flexible distal end portion. A proximal end of the stiffening member may float within a distal end of the proximal cannula, but the stiffening member distal end is affixed to the shaft. The dilatation catheter may have a rapid exchange configuration, and is generally used in conjunction with a guiding catheter. During a procedure when the catheters are within the vascular system, the transition section of the dilatation catheter readily follows curved portions of the inserted guiding catheter.

REFERENCE TO RELATED APPLICATION

[0001] This application is a Divisional of 09/594,859 filed Jun. 15,2000.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention generally relates to a balloon catheter forconducting dilatation procedures within the vascular system. The ballooncatheter may be used in conjunction with a guiding catheter, withinwhich the balloon catheter is slidably moved for positioning andtreatment. The balloon catheter includes an elongated, high-strengthcannula or hypotube as a proximal tube component. The catheter has adistal end assembly which includes the balloon and which has asubstantially greater flexibility than that of the proximal cannula. Theproximal cannula and the distal end assembly are joined together by atransition assembly which has a stiffening element. The presentinvention improves various performance features of the catheter,including trackability, pushability, flexibility, etc.

[0003] In many applications for dilatation catheters, it is desirable toprovide a proximal catheter tube which is relatively stiff and of highstrength so that the elongated proximal tube accepts and transmitscolumn force, as well as torsional forces, from the proximal end of thecatheter which remains outside of the body, to the distal end portion ofthe catheter so that the balloon is properly positioned for performingthe dilatation procedure.

[0004] Proximal elongated tubes such as metal hypotubes have beenproposed or used in the past for balloon catheter shafts. However, thistype of stiff tubing preferably does not extend the full length of theballoon catheter. In order to maneuver through tight turns and/orconstricting passageways, the distal end portion of the catheter shouldbe quite flexible.

[0005] While having a stiff proximal hypotube and a flexible distalportion has been a desirable objective, achieving this objective iscomplicated by the need for providing a suitable transition between arelatively stiff elongated member and a relatively flexible elongatedmember. As used in this patent, the term “elongated” refers simply tohaving a measurable length, as opposed to implying any stretching orprocess that might otherwise be considered “elongation”. It has beenfound that, when two such diverse stiffness sections interface directlywith each other, there is a tendency that the catheter may kink orprolapse on itself during movement of the balloon catheter with respectto the guiding catheter. Accordingly, the balloon catheter may not moveconsistently and smoothly through the guiding catheter, or even reachthe desired site. At times, the guiding catheter may dislodge from itsdesired position within the vascular system of the body.

[0006] In the past, catheters of this general type have included atransitional section between a stiff hypotube type of component and aflexible distal end portion of the catheter. A primary component ofthese types of transitional section approaches is the incorporation of astructure having selected flexibility or range of flexibilitiesgenerally at the transition location, whereby the stiffness at theproximal hypotube is gradually reduced toward the flexible distalportion of the catheter. In some known systems, a bridging wire isattached to the hypotube as a distally oriented extension of thehypotube, positioned within a transition section between the hypotubedistal end and the distal portion of the catheter with the balloon.

[0007] With approaches such as those generally identified above, thebridge wire or a similar structure may present challenges when theballoon catheter must be passed through a tightly curved portion of theguiding catheter. There may be a tendency for the bridge wire totransfer a bending or lateral force to the walls of the guidingcatheter, due to the stiffness of the bridging wire, which lateral forcetypically increases when the tightness of the curve increases.

[0008] It is accordingly desirable for a catheter system to have aballoon catheter which will easily navigate tight curves in the distalportion of the guiding catheter without imparting undue lateral force tothe walls of the guiding catheter, which could possibly result inunintentional dislodgement of the guiding catheter due to movement ofthe balloon catheter. Accordingly, the present invention concentrates onthe structure of a transition section between a relatively stiffproximal tube and a relatively flexible distal portion.

[0009] The present invention can also be relevant in catheters having arapid exchange configuration, which incorporate a guidewire lumen onlyat a distal end portion of the catheter. Such an overall structurepermits the physician to easily and rapidly exchange one ballooncatheter for another, and generally avoids the need for extended orextendable length guidewires, and the issues associated with providingand handling them. Balloon catheter systems of this general type areshown in Yock U.S. Pat. No. 5,061,273 and Leopold U.S. Pat. No.5,346,505, and their subject matter is incorporated herein by reference.Generally, by providing a guidewire exit port in a generally distalportion of the catheter, it can intensify the possibility of undesiredweakness or sharp flexibility transitions of the catheter. Such weaknessmay be caused by abrupt flexibility differences between a distal sectionof the catheter having the guidewire tube and guidewire, and a proximalsection of the catheter immediately proximal of the guidewire exit port.There is accordingly a preference for an improved transition structurein balloon catheters generally, and in the vicinity of the guidewireexit port of balloon catheters having a rapid exchange configuration.

[0010] In accordance with the present invention, a balloon dilatationcatheter has an improved transition assembly between a relativelyhigh-strength proximal cannula and a generally tubular distal endassembly, which is substantially more flexible than the proximalcannula. The transition assembly provides flexible bending strain reliefhaving optimized flexibility, column strength, pull strength, and othercharacteristics. The transition assembly preferably includes astiffening member within a transition tube.

[0011] Moreover, the stiffening member may preferably be attached to thecatheter shaft near its distal end, and float relatively freely in thecatheter shaft at its proximal end.

[0012] This balloon dilatation catheter will often be used incombination with a guiding catheter, so the balloon dilatation catheteris able to smoothly follow sharp curves of the guiding catheter, whichmay be encountered during a dilatation procedure such as angioplasty.With this combination, the transition assembly is optimized to impart aminimal lateral force on the guiding catheter, so as to avoiddislodgement of the guiding catheter from its intended position in thevascular system, as the dilatation catheter is moved within the guidingcatheter.

[0013] Accordingly, a general possible object of the present inventionis to provide an improved balloon dilatation catheter, combination ofdilatation catheter and guiding catheter, and method for making theballoon dilatation catheter.

[0014] Another possible object of this invention is to provide animproved balloon catheter having a transition assembly, which providesflexible bending strain relief during medical procedures.

[0015] Another possible object of the present invention is to provide animproved combination of balloon dilatation catheter and guidingcatheter, such that during slidable positioning of the balloondilatation catheter within the guiding catheter, the transition sectionreadily bends in an arc, thereby minimizing the lateral force applied tothe guiding catheter and avoiding dislodgement of the guiding catheterfrom the desired position.

[0016] Another possible object of this invention is to provide a balloondilatation catheter which moves linearly in the distal direction insideof a guiding catheter, without undesired flexing of the transitionassembly, which could hinder transmission of forces from the proximalend of the catheter outside the body to the distal end of the catheterinside the patient's body.

[0017] Another possible object of the present invention is to provide animproved balloon dilatation catheter and guiding catheter combination,which reduces the chance of having the guiding catheter become dislodgedfrom the desired position during an angioplasty procedure.

[0018] Another possible object of this invention is to provide a balloondilatation catheter having a transition section which reduces theincidence of kinking the catheter.

[0019] Another possible object of the present invention is to provide animproved balloon dilatation catheter and guiding catheter combination,which exhibits an advantageous ease of tracking and lower trackingforce, due to having an improved transition section which forms to theshape of the guiding catheter when that transition section moves throughthe guiding catheter.

[0020] Another possible object of the present invention is to provide atransition section for a balloon dilatation catheter which provides arelatively larger cross-sectional area for passage of balloon inflationfluid during balloon inflation and deflation.

[0021] These and other possible objects, features and advantages of thepresent invention will be apparent from and clearly understood through aconsideration of the following detailed description of the preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the course of this description of preferred embodiments,reference will be made to the attached drawings, wherein:

[0023]FIG. 1 is a partially schematic generally elevational view of apreferred balloon dilatation catheter in accordance with the principlesof the present invention;

[0024]FIG. 2 is an enlarged, substantially cross-sectional viewincluding the transition section of the catheter generally illustratedin FIG. 1, shown positioned within a guiding catheter, partially cutaway and shown in transverse cross-section;

[0025]FIG. 3 is a cross-sectional view along the line 3-3 of FIG. 1;

[0026]FIG. 4 is a cross-sectional view along the line 4-4 of FIG. 1;

[0027]FIG. 5 is a cross-sectional view along the line 5-5 of FIG. 1;

[0028]FIG. 6 is a generally diagrammatic partial view of the distal tipportion of the catheter of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The following description of the preferred embodiments of thepresent invention is merely illustrative in nature, and as such it doesnot limit in any way the present invention, its application, or uses.Numerous modifications may be made by those skilled in the art withoutdeparting from the true spirit and scope of the invention.

[0030] A preferred balloon dilatation catheter is generally designatedin FIG. 1 by reference numeral 10. It includes a proximal hub assembly12 of generally known structure for manipulating the catheter 10 from alocation outside of the patient's body in a manner which is generallyknown in the art. An elongated, high strength proximal cannula orhypotube 14 is attached to the hub assembly 12 by a suitable structureand approach. A distal end assembly including a balloon, generallydesignated at 16, provides the distal portion of the catheter 10. Atransition assembly, generally designated at 18, connects the flexibledistal end assembly 16 to the proximal cannula 14. A guiding catheter 20is generally depicted in FIG. 2 in sliding engagement with the balloondilatation catheter 10.

[0031] With more particular reference to the proximal cannula 14, it ispreferably made of a hypotube, typically made of metal. Some especiallystiff polymers can also be used. Hypotubes include those made ofstainless steel, other stiff alloys available for use within the body,nickel-titanium alloys such as nitinol, and similar materials. Theproximal cannula 14 incorporates a material and structure which providesexcellent load-bearing properties, including high column strength andexcellent torqueability. Properties such as these permit a physician toaccurately manipulate the substantial proximal length of the catheterwhile the catheter is inserted within and through the vascular system ofthe patient. Such a high-strength cannula 14 also provides responsivemovement of the more distal portions of the catheter 10 in response tomovements such as twisting and longitudinal movements in and out withinthe vascular system.

[0032] It will be appreciated that maneuvering control at this proximalportion of the balloon dilatation catheter 10 enhances the performancecharacteristics of, and imparts an advantageous sure-handed feel to aballoon dilatation catheter. Typically, the length of the elongatedcannula plus the hub assembly is between about 100 cm and about 120 cm.A typical balloon dilatation catheter in accordance with the inventionhas a total length from the hub assembly to the distal tip of about 140cm to about 160 cm.

[0033] Another particular advantage of making the proximal cannula 14 ofa material such as stainless steel or other metal alloy or especiallystrong polymer, is that these materials provide high strength with aminimum wall thickness. Such thin-walled cannulas provide a greatercross-sectional inflation lumen area than do thicker walled tubes,thereby facilitating flow of inflation fluid through the cannula.

[0034] The illustrated distal end assembly 16 includes a balloon 22which is made of a material suitable for a dilatation balloon, and inaccordance with an appropriate molding approach for that material. Theballoon 22 is securely attached to an outer body tube 24, which isattached at its other end to the transition assembly 18. Alternately,distal end assemblies can incorporate dual-lumen tubes having parallelrather than coaxial lumens, for example. The illustrated distal endassembly 16 has a coaxial structure. This coaxial structure includes theouter body tube 24 and an inner body tube or guidewire tube 26. Aproximal leg portion 28 of the balloon 22 is attached to a distalportion of the outer body tube 24. A distal leg portion 30 of theballoon 22 is secured to a distal portion of the inner body tube 26. Thedistal end assembly 16 terminates in a distal tip 32. A typical distalend assembly 16 has a length of several centimeters, for example betweenabout 20 cm and about 30 cm.

[0035] Distal end assembly 16 also includes a guidewire port 34 at itsproximal end. The inner body tube 26 is positioned at this guidewireport 34 so that its proximal opening 36 accommodates a guidewire 38. Itwill be appreciated that, during use of the illustrated catheter 10 andguidewire 38, the guidewire tube and thus the entire balloon dilatationcatheter 10 will be slidably moved with respect to the guidewire 38,after the guidewire 38 has been inserted to the desired location withinthe vascular system. Operation of the equipment in this regard isgenerally known.

[0036] Referring to the illustrated novel transition assembly 18, itincorporates a floating stiffening member 40. This stiffening member 40is typically constructed of flat ribbon wire or a wire that is generallyround in cross-section. The round cross-section is preferred. A braidedor twisted bundle of wires is also possible. Generally, the stiffeningmember 40 can also be made of materials such as those which are suitablefor the proximal cannula 14. Stainless steel is particularly preferred,or possibly nitinol. Stiffening member is preferably designed so thatthe overall transition assembly 18 retains adequate torsional and columnstrengths so that twisting, pushing and pulling forces imparted onto thetransitional assembly 18 by the proximal cannula 14 will not causekinking or permanent twisting of the transitional assembly 18. Inaddition, the flexibility of stiffening member 40 along its lengthshould be selected to provided the desired features and performance,including more smooth flexibility transitions from the proximal cannula14 to the distal portion 16.

[0037] Stiffening member 40 is preferably sealed or affixed at itsdistal end to the catheter shaft, while the stiffening member 40proximal end preferably floats within the distal end of thehigh-strength cannula 14.

[0038] A transition tube 42 surrounds most of the stiffening member 40.A proximal end of the transition tube 42 is affixed to the hypotube 14,and distal end of the transition tube 42 is connected to the outer body24. The transition tube 42 may be typically made of a polymer material.If the tube 42 has good strength attributes, then a less-rigidstiffening 40 member can be provided. Whatever the precise structureutilized, the transition assembly 18 provides a flexible transitionbetween the generally rigid proximal cannula 14 and the generallyflexible distal end assembly 16.

[0039] With more particular reference to the transition tube 42, it ispreferred that the inner diameter of the transition tube 42 define aselected gap distance conforming to the outer diameter of the stiffeningmember 40, while allowing sliding between the surfaces of the wire 40and tube 42 so they slidably engage each other during bending along acurve of the inserted guiding catheter. The stiffening member mayalternatively have one or more tapered locations, and the transitiontube may have its own generally correspondingly shaped and sized taperedlocations. Generally, in making the transition assembly 18, thestiffening member 40 is inserted into the inner diameter or lumen of thetubing 42.

[0040] In the assembly of the stiffening member 40 and the transitiontube 42, the tube 42 is assembled onto the stiffening member 40. In theillustrated embodiment, the proximal end of the transition tube 42 issealed onto the distal end of the proximal cannula 14. The sealing canbe practiced by suitable means, including the use of adhesives and/orheat or other suitable procedures. Similarly, a distal end of thetransition tube 42 extends to the distal end of the stiffening member40, and this distal end is secured to the proximal end portion of thedistal assembly 16 at a distal seal area. Conveniently, the proximalguidewire port 34 is formed when the proximal end portion of theguidewire tube 26 and the stiffening wire 40 distal end are sealedbetween the distal end portion of the transition tube 42 and theproximal end portion of the outer body tube 24.

[0041] In the preferred embodiment, the formation of this distal sealarea is facilitated by having the outer body tube 24 and the transitiontube 42 made of materials which are readily heat-sealed together. Theouter body tube 24 can be made, for example, of a nylon material or of apolyamide material, such as an extruded nylon homopolymer or a copolymeror blend of homopolymer and copolymer. In the preferred embodiment, atleast a portion of the outer surface of the transition tube 42 is madeof a nylon material, and can be made of the same nylon material orpolyamide material as the material of which the outer body tube 24 ismade. Preferably, at least a portion of the inner surface of thetransition tube 42 can be made of a material such as a polyethylene,which more readily bonds to the proximal cannula 14 than does apolyamide or nylon material. In the preferred arrangement, the cannula14 is made of stainless steel, and the outer body tube 24 is made ofnylon 12. In order to accommodate these materials, the transition tube42 is preferably made of two different materials. The preferred mannerof accomplishing this desired result is to have the transition tube 42be formed as a coextrusion. The coextrusion as an example may provide aninner surface of polyethylene, which bonds well to stainless steel, andan external surface of a nylon material or other material which readilybonds to the distal end assembly.

[0042] A typical guidewire tube 26 will preferably accommodate aguidewire 38 having an outer diameter of 0.0014 inch (0.036 mm) when thedilatation catheter 10 is of the percutaneous transluminal catheterangioplasty or PTCA type. When the catheter is, for example, of thepercutaneous transluminal angioplasty or PTA type, the guidewire tube 26will accommodate a guidewire 38 of a larger outer diameter, usually onthe order of 0.0018 inch (0.046 mm). When the stiffening member 40 ismade of a round stainless steel wire, the diameter of the wire 40 may beselected among various sizes.

[0043]FIG. 2 illustrates the stiffening member 40 which extends distallyto an extent which helps to protect and strengthen the proximal endportion of the distal end assembly 16, without unduly stiffening thearea ofjoining between the transition assembly 18 and the distal endassembly 16, including the distal seal area. The distal extent of thestiffening wire 40 also assists in avoiding kinking at this joininglocation where the relatively thick seal area is directly adjacent tothinner tubing lengths.

[0044]FIG. 5 provides a somewhat diagrammatic view of the distal area,in that the transition tube 42 and a short filler tube may actually melttogether.

[0045] Typically, the transition assembly 18 has a total length ofbetween about 10 cm and about 35 cm, preferably between about 12 cm andabout 20 cm. The length of the stiffening member 40 can range betweenabout 5 cm and about 30 cm, preferably between about 8 cm and about 18cm.

[0046] It will be appreciated by those skilled in the art that theguiding catheter 20 and the balloon dilatation catheter 10 can comprisea combination of catheters which are used during balloon dilatationprocedures such as angioplasty, typically in association with aguidewire 38. With the present invention, the interaction of thiscombination of catheters is rendered more beneficial to the physicianperforming a dilatation and/or angioplasty procedure. Without thetransition assembly 18 discussed in accordance with the presentinvention, there may be a tendency for difficulties to arise whenattempting to pass the balloon dilatation catheter through the guidingcatheter at a location where the guiding catheter has a tight curve at alocation along its length within the vascular system and/or heart.

[0047] The transition assembly 18 of the present invention is able tonavigate a tight bend or curve more easily, and thus imparts a lowerlateral force onto the wall of the guiding catheter 20.

[0048] It will be understood that the embodiments of the presentinvention which have been described are illustrative of some of theapplications of the principles of the present invention. Variousmodifications may be made by those skilled in the art without departingfrom the true spirit and scope of the invention.

1. A balloon dilatation catheter for medically treating a patient, comprising: a high-strength proximal tube having proximal and distal ends, and defining a proximal portion of an inflation lumen; a distal shaft assembly defining a distal portion of the inflation lumen in fluid communication with the proximal portion of the inflation humen of the proximal tube, such that the proximal and distal portion of the inflation lumen together define an inflation lumen extending from an inflation port near a proximal end of the catheter to a distal inflation port where the inflation lumen opens into the ballon, the distal shaft assembly further defining a guidewire port from a distal guidewire port near a distal end of the catheter to a proximal guidewire port near a transition between the proximal tube and the distal shaft assembly, the distal shaft assembly having a flexibility greater than the proximal tube; a balloon affixed to the distal shaft assembly near its distal end; and stiffening wire positioned across the transition, providing flexible bending strain relief; the stiffening wire having a portion near its distal end affixed to the distal shaft assembly in a stiffening wire seal area, and the stiffening wire having a proximal end extending into and floating within a distal portion of the proximal lumen defined by the proximal tube.
 2. The dilatation catheter in accordance with claim 1, wherein the distal shaft assembly includes a tube defining the first distal lumen and the guidewire lumen, in a dual-lumen arrangement.
 3. The dilatation catheter in accordance with claim 1, wherein the distal shaft assembly includes an inner and outer tubular body, in a coaxial arrangement.
 4. The dilatation catheter in accordance with claim 3, wherein the stiffening wire is affixed to the inner tubular body near the proximal end of the inner body.
 5. The dilatation catheter in accordance with claim 3, wherein the inner tubular body defines the guidewire lumen, and the portion of the inflation lumen defined by the distal shaft assembly is defined between the inner and outer tubular bodies.
 6. The dilation catheter in accordance with claim 1, wherein the proximal tube is metal, and the distal shaft assembly includes polymer components.
 7. The dilation catheter in accordance with claim 1, further comprising a stent crimped around the balloon in an initial configuration.
 8. A stent delivery system for medically treating a patient, comprising: a high-strength proximal tube having proximal and distal ends, and defining a proximal portion of an inflation lumen; a distal shaft assembly defining a distal portion of the inflation lumen in fluid communication with the proximal portion of the inflation lumen of the proximal tube, such that the proximal and distal portion of the inflation lumen together define an inflation lumen extending from an inflation port near a proximal end of the catheter to a distal inflation port where the inflation lumen opens into the balloon; the distal shaft assembly further defining a guidewire lumen extending from a distal guidewire port near a distal end of the catheter to a proximal guidewire port near a transition between the proximal tube and the distal shaft assembly, the distal shaft assembly having a flexibility greater than the proximal tube; a balloon affixed to the distal shaft assembly near its distal end; and a stiffening wire positioned across the transition, providing flexible bending strain relief; the stiffening wire having a portion near its distal end affixed to the distal shaft assembly in a stiffening wire seal area, and the stiffening wire having a proximal end extending into and floating within a distal portion of the proximal lumen defined by the proximal tube; and a stent crimped around the balloon in an initial configuration.
 9. A balloon dilation catheter for medically treating a patient, comprising: a high-strength proximal tube having proximal and distal ends, and defining a proximal portion of an inflation lumen; a distal shaft assembly including an inner and an outer tubular body, a distal portion of the inflation lumen being defined by an annular space between the inner and outer tubular bodies, such that the distal portion of the inflation lumen is in fluid communication with the proximal portion of the inflation lumen defined by the proximal tube; the proximal and distal portions of the inflation lumen together defining an inflation lumen extending from an inflation port near a proximal end of the catheter to a distal inflation port where the inflation lumen opens into the balloon; the inner tubular body defining a guidewire lumen extending from a distal guidewire port near a distal end of the catheter to a proximal guidewire port near a transition between the proximal tube and the distal shaft assembly, the distal shaft assembly having a flexibility greater than the proximal tube; a balloon affixed to the distal shaft assembly near its distal end; and a stiffening wire positioned across the transition, providing flexible bending strain relief; the stiffening wire having a protion near its distal end affixed to the inner tubular body in a stiffening wire seal area, and the stiffening wire having a proximal end extending into and floating within a distal portion of the proxmial lumen defined by the proximal tube. 